Flexible couplings are known which comprise an annular body, typically of a plastics material, incorporating circumferentially spaced, parallel bores through which bolts can be passed to bolt the coupling to an annular flange on the drive shaft and to an annular flange on the driven shaft. The body has an even number of fastening means providing bores and alternate bolts connect the body to the one and then the other flange. Adjacent bores are linked so that as each bolt connected to the flange on the drive shaft moves it drags with it the bolt upstream of it connected to the flange on the driven shaft. The body is substantially inelastic but has a degree of flexibility, and this permits minor misalignment between the shafts without destruction of the coupling. The fastening means providing the bores may be bushes connected by strands passed around and between them, but conveniently may be constituted by, or may comprise, apertures at opposite ends of metal links. An even number of links is “stacked” with the apertures at one of their respective ends in alignment and the apertures at the other of their respective ends located alternately at the adjacent fastening means on opposite sides of the first-mentioned fastening means. Washers are located on opposite sides of each “stack” of links to provide end orifices for the bores.
The problem arises that when a bolt is subsequently pushed through a bore of a previously manufactured coupling it is liable to push the downstream washer out of the body of the coupling, the bond between the washer and the plastics material of the body being insufficient to prevent this.
An object of the present invention is to overcome this problem by keying the washers to the body so that only a force sufficient to shear the material of the body would be great enough to allow a washer to be expelled. In practice forces of this magnitude will not be encountered.